The core of the Distutils. Most of the work hiding behind 'setup'
is really done within a Distribution instance, which farms the work out
to the Distutils commands specified on the command line.

Setup scripts will almost never instantiate Distribution directly,
unless the 'setup()' function is totally inadequate to their needs.
However, it is conceivable that a setup script might wish to subclassDistribution for some specialized purpose, and then pass the subclass
to 'setup()' as the 'distclass' keyword argument. If so, it is
necessary to respect the expectations that 'setup' has of Distribution.
See the code for 'setup()', in core.py, for details.

Construct a new Distribution instance: initialize all the
attributes of a Distribution, and then use 'attrs' (a dictionary
mapping attribute names to values) to assign some of those
attributes their "real" values. (Any attributes not mentioned in
'attrs' will be assigned to some null value: 0, None, an empty list
or dictionary, etc.) Most importantly, initialize the
'command_obj' attribute to the empty dictionary; this will be
filled in with real command objects by 'parse_command_line()'.

Find as many configuration files as should be processed for this
platform, and return a list of filenames in the order in which they
should be parsed. The filenames returned are guaranteed to exist
(modulo nasty race conditions).

There are three possible config files: distutils.cfg in the
Distutils installation directory (ie. where the top-level
Distutils __inst__.py file lives), a file in the user's home
directory named .pydistutils.cfg on Unix and pydistutils.cfg
on Windows/Mac, and setup.cfg in the current directory.

Return the class that implements the Distutils command named by
'command'. First we check the 'cmdclass' dictionary; if the
command is mentioned there, we fetch the class object from the
dictionary and return it. Otherwise we load the command module
("distutils.command." + command) and fetch the command class from
the module. The loaded class is also stored in 'cmdclass'
to speed future calls to 'get_command_class()'.

Raises DistutilsModuleError if the expected module could not be
found, or if that module does not define the expected class.

Get a list of (command, description) tuples.
The list is divided into "standard commands" (listed in
distutils.command.__all__) and "extra commands" (mentioned in
self.cmdclass, but not a standard command). The descriptions come
from the command class attribute 'description'.

Return the command object for 'command'. Normally this object
is cached on a previous call to 'get_command_obj()'; if no command
object for 'command' is in the cache, then we either create and
return it (if 'create' is true) or return None.

Get the option dictionary for a given command. If that
command's option dictionary hasn't been created yet, then create it
and return the new dictionary; otherwise, return the existing
option dictionary.

Parse the setup script's command line, taken from the
'script_args' instance attribute (which defaults to 'sys.argv[1:]'
-- see 'setup()' in core.py). This list is first processed for
"global options" -- options that set attributes of the Distribution
instance. Then, it is alternately scanned for Distutils commands
and options for that command. Each new command terminates the
options for the previous command. The allowed options for a
command are determined by the 'user_options' attribute of the
command class -- thus, we have to be able to load command classes
in order to parse the command line. Any error in that 'options'
attribute raises DistutilsGetoptError; any error on the
command-line raises DistutilsArgError. If no Distutils commands
were found on the command line, raises DistutilsArgError. Return
true if command-line was successfully parsed and we should carry
on with executing commands; false if no errors but we shouldn't
execute commands (currently, this only happens if user asks for
help).

Print out a help message listing all available commands with a
description of each. The list is divided into "standard commands"
(listed in distutils.command.__all__) and "extra commands"
(mentioned in self.cmdclass, but not a standard command). The
descriptions come from the command class attribute
'description'.

Reinitializes a command to the state it was in when first
returned by 'get_command_obj()': ie., initialized but not yet
finalized. This provides the opportunity to sneak option
values in programmatically, overriding or supplementing
user-supplied values from the config files and command line.
You'll have to re-finalize the command object (by calling
'finalize_options()' or 'ensure_finalized()') before using it for
real.

'command' should be a command name (string) or command object. If
'reinit_subcommands' is true, also reinitializes the command's
sub-commands, as declared by the 'sub_commands' class attribute (if
it has one). See the "install" command for an example. Only
reinitializes the sub-commands that actually matter, ie. those
whose test predicates return true.

Do whatever it takes to run a command (including nothing at all,
if the command has already been run). Specifically: if we have
already created and run the command named by 'command', return
silently without doing anything. If the command named by 'command'
doesn't even have a command object yet, create one. Then invoke
'run()' on that command object (or an existing one).